如何修改此订购？

Question

我有这段代码调用了Longs的默认比较器：

val ordering = implicitly[Ordering[Long]]

如何创建自己的订单并使用implicitly调用？

我尝试过：

trait MyOrdering extends Ordering[Long] {
  override def compare(x: Long, y: Long): Int = x compare y
}

val ordering = implicitly[MyOrdering]

但这不起作用

Answer 1

您需要将新的Ordering实现的实例放入隐式命名空间。

implicit val mo :MyOrdering = new MyOrdering {}

val ordering = implicitly[MyOrdering]

您也可以将trait更改为implicit object，但还需要修改implicitly参数。

implicit object MyOrdering extends Ordering[Long] {
  override def compare(x: Long, y: Long): Int = x compare y
}

val ordering = implicitly[MyOrdering.type]